# Choosing the most suitable testing method to compare 2 population means

I am doing a sales performance analysis of different products and need to compare the weekly average sales of 2 products to see if one is still higher than the other (Sales of product A is higher than that of B in the past and I want to check if that is still the case). I have the data of sales collected by each period (13 periods), by each store that sold our products (3 stores) and by each week (52 weeks).

The problem is that if I choose the sampling is by week, the sample size is only 3 (1 value for each store) and that makes it fail to follow the normality assumption for two samples t-test.

If I choose to sample by period, the sample size is 13. I tested the normality using Anderson-Darling test and obtain the p-value of 0.1 and 0.2 respectively for each product A and B, which are still greater than 0.05 and I think I could continue with the two sample t-test. But I don't know if I can choose samples by period since the question is to compare average weekly sales.

So my questions are:

1. Could I choose to sample by period instead of by week even though the question is to compare average weekly sales?
2. Should I choose to implement a non-parametric alternative instead of two samples t-test? Which are the most suitable test for this problem?